Williams technical director Sam Michael insisted the team's first day of running with the new FW33 in Valencia had been 'positive', despite the fact that Rubens Barrichello was hit with a KERS issue during the morning running.

Despite the problem, Barrichello was able to complete more than 70 laps in the car, which is running in an interim livery ahead of an official launch at a date still to be announced.

That allowed the team to complete a number of checks that had been planned and Michael insisted it has been a positive day at the Spanish circuit.

"It's been a good day in terms of getting through things," he said. "We had a problem with KERS this morning so we didn't use it in the afternoon. Besides that, everything else on the car is working and we didn't have any problems with temperatures, pressures and all the systems are working fine.

"We now plan to do more mileage and setup work tomorrow. The moveable rear wing also worked fine today so all in all a pretty good first day."

Barrichello himself was also happy with the day despite the delay to his programme.

"I couldn't wait to get back in the car," he said. "Unfortunately we lost a lot of time in the morning so we were trying to play catch up in the afternoon. We did some good laps and some long runs in the car. It is too early to say how we are performing but we will now spend time to try and understand the car a little better."

Barrichello is back in the car again today before handing over to team-mate Pastor Maldonado tomorrow.